Measurement configuration for A3 event in advance

Is it possible to do measurement configuration for a3 event much in advance?

  1. UE attached to LTE1 cell.
  2. Measurement configuration for a3 event by LTE1 cell.
  3. Measurement configuration for b1 event to add NR cell
  4. NR cell added.
  5. A3 event triggered upon better signal from LTE2 cell and handovered to LTE2 cell.

Here measurement configuration is done in step2 and a3 triggered in step5 .Is this possible?

It’s possible after scg addition still UE can do HO for mcg cells which happened here as per radio conditions.

But without releasing measurement gap for A3, can it perform measurement configuration for B1 event?

In my view meas gap config common for LTE and NR I sent 1 table …so if gap 0,1 etc there then it can be used for a3 and b1.

Mgap 1, 2 can be use to measure both LTE and NR.
So in this case LTE mgap is used for NR also.SMTC for NR falls in to mgap.

So it means between step2 and step5.
UE can start measuring LTE2 from step2 and continue till step5?
Because in parallel it is measuring NR cell, receiving b1 event and releasing measurement gap for b1 and adding NR cell.

Seems a3 measured by UE in step 5 as it’s hold good till time to trigger radio conditions keep satisfy as per A3 offset for neighbour cell.
For detail you can see logs when UE enter in A3 state.

Will UE start measurements just at step2? I doubt it.

UE will start measurements in mgap period when it comes and will keep switching between to tx and measurements.

Otherwise, how can step 3 will be communicated to UE?

Yes it’s possible.

UE will measure and report, it is up to eNB to take further action.


  1. UE attaches to LTE1 cell.
  2. Network configures UE to measure LTE2 cell for A3 report
  3. Network configures UE to measure NR1 cell for B1 report.
  4. B1 report of NR1 is received.
  5. Measurement gap for B1 is released.
  6. NR1 cell is added and now UE is talking to the EN DC cell.
  7. Now A3 report of LTE2 is received by network.
  8. Measurement gap for A3 is released.
  9. UE is handovered to LTE2.

So this will be the flow?
Is my understanding correct?

You can add in step 2 value for mgap as well …rest all looks ok.


  • LTE2 cell is interfrequency cell
  • NR: FR1

In this case, step 5 may not required.
Because single mgap can work for LTE and NR.

In step 5 event B1 is removed and event A2 for SCG release can be configured to UE.

Why we need scg release here to trigger A3?
In my view HO from mcg1 to mcg2 can be done without scg release.

SCG release and MCG handover are independent things.
I just mention what can contain in step 5.

Yes we have new feature in NR ie A2 based sgnb release.

Once UE move to poor radio conditions on basis of A2 sgnb release it.

Yes LTE 2 is interfrequency and NR1 is FR1.

Actually testplan mentions specifically about seperate B1 meas config from network.

They have mention separate B1 measurement config.
Not separate measurement gap config.

Yes correct.